This invention relates to an apparatus for operating a discharge lamp by applying a transistor inverter.
A known apparatus for operating a discharge lamp is also provided with a transistor inverter. With the prior art apparatus, power supplied from a D.C. source is converted by a transistor inverter into A.C. power having a frequency ranging from several KHz to scores of KHz. This A.C. power actuates a discharge lamp. In this case, part of the A.C. power heats a pair of electrodes received in the discharge lamp. In this case, high frequency A.C. voltage is impressed across the paired electrodes at the commencement of their heating. In other words, the conventional discharge lamp operating apparatus has such arrangement that high voltage is supplied to the paired electrodes, before they are fully preheated. Consequently, the electrodes are damaged in a relatively short time, unavoidably resulting in the short effective life of a discharge lamp. Particularly where a discharge lamp is started and operated on a full scale by the aforesaid high frequency power, a start voltage applied across the paired electrodes should have a higher level than when the discharge lamp is started and put into full operation by power having a commercially specified frequency. As a result, the electrodes are noticeably depleted.
It is accordingly the object of this invention to provide an apparatus for operating a discharge lamp, which makes it possible to apply a lower voltage than required in the past across the paired electrodes during a prescribed period in which the electrodes are preheated.